Anatomical Terminology and Position

Objectives of Anatomical Terminology

• Define the anatomical position
• Identify reference planes to locate body structures
• Use anatomical terminology to describe body directions, regions, and planes
• Use descriptive and directional terms referring to the body correctly

Anatomical Position

• Visual reference point used to describe body parts/locations accurately
• A person stands erect with feet parallel to each other
• Feet are on the floor: arms are at sides, palms face anteriorly, fingers point straight down
• Thumbs point away from the body, face and eyes face forward

Importance

• Most directional terminology in anatomy is based on the body in this position
• All direction terms describing relationships between body parts reference the anatomical position

Right and Left

• Terms "right" and "left" refer to the subject being viewed, not the viewer

Body Regional Terms

• Specific names designate body areas
• Knowledge of external anatomy and landmarks is important for physical examinations and clinical procedures

Fundamental Divisions of the Body

• Axial region: main body axis, including the head, neck, and trunk
• Trunk: divided into thorax (chest), abdomen, and pelvis
• Appendicular region: upper and lower limbs (appendages or extremities)

Common Terms

• Abdominal: region between the thorax and pelvis
• Antebrachial: forearm
• Antecubital: front of the elbow
• Axillary: armpit
• Brachial: upper arm
• Celiac: abdomen
• Cephalic: head
• Cervical: neck
• Costal: ribs
• Cubital: elbow
• Femoral: thigh
• Gluteal: buttock
• Lumbar: lower back

Body Cavities

• Spaces within the body that house the internal organs.
• Help protect, separate, and support internal organs
• Bones, muscles, and ligaments separate the various body cavities.

Orientation and Directional Terms

• Medical personnel and anatomists use standard directional terms to describe the position of body structures relative to one another
• Frequently used paired terms include superior/inferior, anterior/posterior, medial/lateral, and superficial/deep

Superior (Cranial)

• Towards the head end or upper part of a structure, or the body
• Above

Inferior (Caudal)

• Away from the head end or toward the lower part of a structure, or the body
• Below

Anterior (Ventral)

• Toward or at the front of the body
• In front of

Posterior (Dorsal)

• Toward or at the back of the body
• Behind

Medial

• Toward or at the midline of the body
• On the inner side of

Lateral

• Away from the midline of the body
• On the outer side of

Proximal

• Closer to the origin of the body part
• Point of attachment of a limb to the body trunk

Distal

• Farther from the origin of a body part
• Point of attachment of a limb to the body trunk

Superficial (External)

• Toward or at the body surface

Deep (Internal)

• Away from the body surface
• Toward the inside of a structure

Ipsilateral

• On the same side

Contralateral

• Refers to the opposite sides.

Ventral

• Towards the front or belly

Dorsal

• Towards the back or spine

Cephalic

• Towards the head or superior end.

Rostral

• Towards the forehead or nose.

Caudal

• Towards the tail or inferior end.

Central

• A body part is situated at the center of the body or an organ
• The central nervous system is along the main axis of the body

Peripheral

• A body part is situated away from the center of the body or an organ
• The peripheral nervous system is outside the central nervous system

Invagination

• Inward protrusion

Evagination

• Outward protrusion

External

• Towards the outside of a structure
• Used when describing relationships of individual organs
• Visceral pleura is on the external surface of the lungs

Internal

• Towards the inside of a structure
• Used when describing relationships of individual organs
• The mucosa forms the internal lining of the stomach

Body Anatomical Planes and Sections

• In anatomy, the body is sectioned (cut) along a flat surface called a plane
• Section implies an actual cut or slice to reveal internal anatomy
• Plane implies an imaginary flat surface passing through the body

Common Body Planes

• Sagittal
• Frontal
• Transverse

Characteristics of Body Planes

• Lie at right angles to one another
• A frontal (coronal) plane extends vertically and divides the body into anterior and posterior parts
• A transverse (horizontal) plane runs horizontally from right to left, dividing the body into superior and inferior parts. Is also called a cross sectional
• Sagittal planes extend vertically and divide the body or an organ into right and left parts
• CT scans, MRIs, and X-rays are usually taken in these planes

Axes

• Three main axes run perpendicular to each other in three spatial coordinates
• Longitudinal axis (vertical, cephalocaudal axis): runs perpendicular to the base in the upright posture
• Horizontal axis (transverse axis): runs from left to right perpendicular to the longitudinal axis
• Sagittal axis: runs from front to back and perpendicular to both other axes

Thoracic and Abdominal Cavity Membranes

• A membrane is a thin pliable tissue that covers, lines, partitions, or connects structures
• A slippery double-layered membrane is called a serous membrane
• Covers the viscera within the thoracic and abdominal cavities
• Lines the walls of the thorax and abdomen

Parts of a Serous Membrane

• Parietal layer: thin epithelium lining the walls of the cavities
• Visceral layer: thin epithelium covering and adheres to the viscera within the cavities

Serous Sac Formation

• Parietal and visceral membranes are continuous with one another, forming a serous sac
• A small amount of lubricating (serous fluid) within the serous cavity reduces friction between the two layers

Functioning of the Viscera

• Allows the viscera to slide during movements such as pumping of the heart and inflation/deflation of lungs

Pleura

• The serous membrane associated with the lungs
• Visceral pleura clings to the surface of the lungs

Parietal Pleura

• Lines the chest wall
• Covers the superior surface of the diaphragm
• Has a pleural cavity in between, filled with a small volume of lubricating fluid (serous fluid)

Pericardium

• Serous membrane of the heart
• Visceral pericardium covers the surface of the heart
• Parietal pericardium lines the fibrous pericardium that surrounds the heart
• Pericardial cavity in between which contains a small amount of lubricating fluid

Peritoneum

• Serous membrane of the abdominal cavity
• Visceral peritoneum covers the abdominal viscera
• Parietal peritoneum lines the abdominal wall and covers the inferior surface of the diaphragm
• Peritoneal cavity in between has a small amount of lubricating fluid
• Most abdominal organs are surrounded by the peritoneal cavity and are referred to as intraperitoneal

Intraperitoneal Organs

• Stomach
• Spleen
• Liver
• Gallbladder
• Jejunum and ileum of the small intestine
• Cecum
• Appendix
• Transverse colon of the large intestine

Retroperitoneal Organs

• Some organs are located between the parietal peritoneum and the posterior abdominal wall

Examples of Retroperitoneal Organs

• Kidneys
• Adrenal glands
• Pancreas
• Duodenum of the small intestine
• Ascending and descending colons of the large intestine
• Abdominal aorta and inferior vena cava

Abdominopelvic Regions and Quadrants

• To describe the location of abdominal and pelvic organs easily, anatomists and clinicians use 2 methods of dividing the abdominopelvic cavity into smaller areas

First Method of Division

• Partition the cavity into 9 abdominopelvic regions using 2 transverse and 2 vertical lines
• Superior horizontal line uses the subcostal line, passing across the lowest level of the 10th costal cartilages
• Some use the transpyloric line that is halfway between the suprasternal notch of the manubrium and the upper border of the pubic symphysis at the level of the 1st lumbar vertebrae, and also crosses the tip of the 9th costal cartilage

Second Method of Division

• The inferior horizontal line which uses transtubercular line, that passes across the superior margins of the iliac crests of the right and left hip bones
• The 2 vertical lines which use the left and right midclavicular lines, are drawn through the midpoints of the clavicles(collar bones), just medial to the nipples

Nine Abdominopelvic Regions

• Divide the cavity into a larger middle section and smaller left and right sections using dividing lines
• The regions are called: right hypochondriac, epigastric, left hypochondriac, right lumbar, umbilical, left lumbar, right inguinal (iliac), hypogastric (pubic), and left inguinal (iliac)

Second Method

• Simpler and divides the abdominopelvic cavity into four quadrants
• A transverse line- transumbilical line
• A midsagittal line (median line) are passed through the umbilicus
• The quadrants are right upper (RUQ), left upper (LUQ), right lower (RLQ), and left lower (LLQ)

Utility of Divisions

• Anatomical studies use the nine-region division more widely to determine organ location
• Clinicians use the quadrants division to describe the site of abdominopelvic pain, tumor, injury, or other abnormality

Noninvasive Diagnostic Techniques

• Health-care professionals and students commonly assess certain aspects of body structure and function

Noninvasive Diagnostic Technique

• Diagnostic technique that does not involve inserting an instrument or device through the skin or into a body opening

First Noninvasive Diagnostic Technique

• Inspection involves the examiner observes the body for any changes that deviate from normal
• Visually observing the body to note any clinical symptoms, such as abnormal skin colour, swelling, or rashes
• For example, a physician may examine the mouth cavity for evidence of disease
• Other observations may include needle marks on the skin, irregular breathing rates, or abnormal behaviour

Palpation

• The examiner feels body surfaces with the hands, and applies the fingers with firm pressure
• Helps to feel surface landmarks, lumps, tender spots, or pulsations
• Palpating the neck detects enlarged or tender lymph nodes

Auscultation

• The examiner listens to body sounds to evaluate the functioning of certain organs
• A stethoscope amplifies the sounds
• Listening to organ sounds such a breathing, heartbeat, digestive sounds

Percussion

• During percussion the examiner taps on the body surface with the fingertips
• Listens to the resulting echo
• Aids in locating excess fluids or organ abnormalities
• May reveal abnormal presence of fluid in the lungs or air in the intestines
• Reveals the size, consistency, and position of an underlying structure

Anatomical Terms of Movement

• Actions of muscles on the skeleton are described using specific terms
• Muscles contract to produce movement at joints

Common Movements

• Flexion
• Extension
• Abduction
• Adduction
• Rotation
• Circumduction
• Pronation
• Supination
• Dorsiflexion
• Plantar flexion

Flexion

• This movement occurs in the sagittal plane
• Decreases the angle between two body parts

Extension

• This movement also occurs in the sagittal plane
• Refers to a movement that increases the angle between two body parts

Abduction

• Refers to movement of a body part away from the midline or midsagittal plane

Adduction

• Refers to movement towards the midline

Rotation

• Medial rotation(internal rotation): describes movement of the limb around their long axis, a rotational movement towards the midline
• Lateral rotation(external rotation):describes movement of the limb around their long axis, a rotating movement away from the midline

Circumduction

• A complex movement that combines flexion, abduction, extension, and adduction in succession

Opposition

• Action by which you move your thumb across the palm enabling it to touch the tips of the other fingers on the same hand

Inversion and Eversion

• Special movements of the foot

Inversion

• The sole of the foot faces medially

Eversion

• Movement in which the sole of the foot faces outward or laterally

Dorsiflexion

• Movement at the ankle
• Lifting the foot so that its superior surface approaches the shin

Plantar flexion

• Movement at the ankle
• Depressing the foot or elevating the heel (pointing the toes)

Protraction

• Nonangular movements in the anterior direction
• Movement of a bone anteriorly (forward) in the horizontal plane

Retraction

• Nonangular movements in the posterior direction